@ Bud Johns -

For reference, the smallest gasoline-powered variant of the S-Class as sold in Germany today is called the S350. It features a 3.5L V6 rated at 200kW/350Nm that gets 10.2 L/100km.

With the microhybrid masking the turbo lag to some extent, a DiesOtto would be comparable in daily driving where low-end torque matters most and, improve fuel economy by a whopping 40%. People don't drive S-Classes to hoon around, so they'll never even notice that the rated power rated power is 12% lower. Indeed, anyone looking at a DiesOtto will most likely be cross-shopping it against a comparable conventional diesel, if one is available.

The real problem with downsizing is one of consumer perception: marketing departments have spent decades convicing customers that more displacement and more cilinders equals more power and more prestige. Saving fuel first and foremost implies pinching pennies. S-Class owners are not misers, though many are businesspeople who didn't get rich by throwing money down the drain. Still, once this technology does go into production, expect the sales pitch to focus on reduced CO2 emissions and/or improving energy security, depending on the customer's political persuasion.

"I would think it could do better than that. 295 ft lb of torque is huge for this size engine."

Really? That's a 1.8 liter engine that is within 5ft/lbs of the new BMW 3.0 Twin Turbo with GDI. That sounds pretty good to me.

Rafeal has some cute throw away lines but not much substance.

Any engine running two distinct combustion modes is not a smart idea. I find these outrageous claims of achieving Diesel efficiency nonsense. The fact is that this engine can neither run as lean and at as high a CR as a Diesel engine for as much of the speed and load range.

As Rafeal knows only too well Germans regularly drive at full load on the autobahns so this concept is still not as good as the current Diesels, rather much worse for real world autobahn fuel consumption.

In any event this will make a good display at the IAA and have many people believing that it is the next big deal in engine technology. I pity the poor devils who have to bring this to serial production...

extracomment,

here's some extracomments for you:
GDI (with modestly higher compression ratio) can run lean and powerful due to stratified-charge arrangement. Remember that at a given compression ratio, Otto cycle (isochoric combustion) is significantly more efficient than Diesel cycle (isobaric combustion). A GDI SI does not need to have as high a compression ratio as a Diesel in order to attain the same thermal efficiency.

In fact, the high compression ratio of the Diesel increases engine friction at part load in comparison to an Otto cycle engine at part load. HCCI at part load gives you dual benefit of Diesel efficiency without associated Diesel's costly disadvantage. This is a very impressive development!

If you don't much care for all the extra power of this Mercedes engine, you can go the Ford approach in the previous HCCI article and use low-cost port fuel injection and conventional 3-way exhaust catalytic converter (instead of more expensive Blue-tec to reduce NOx and particle filter for PM in Diesel and for GDI engine operating in lean stratified charge mode).

I wonder if this technology could be integrated with ethanol injection to increase efficiency further

http://www.greencarcongress.com/2006/05/ethanol_direct_.html

HCCI technology has actually made it into street legal vehicles before. Honda has played with it in 2-cycle street/trail bikes. They call it "Activated Radical combustion," and like the Mercedes design, it switches between SI and autoignition. I believe it was used in the exp-2 as well as the NX400, and the CRM250AR which was/is a production bike. They claim the emissions were better than the current 4-stroke offerings. I realize that the dynamics with 2-cycles and 4-cycles are quite different, but I have to wonder why Honda hasn't been publicly pursuing HCCI technology in LDV's considering the experience they already have with motorcycles, and the fact that they seem to be lagging Toyota on the hybrid front. Honda has built fuel efficient vehicles since day one, and if I'm not mistaken, they still sell the most fuel efficient fleet in the US, but they seem to be conspicuously absent from the news these days with regard to fuel saving technology in passenger cars.

GDI (with modestly higher compression ratio) can run lean and powerful due to stratified-charge arrangement. -- Roger Pham

With the same requirement for "costly" NOx treatment.

Remember that at a given compression ratio, Otto cycle (isochoric combustion) is significantly more efficient than Diesel cycle (isobaric combustion).

But not running stratified charge (where you would have all that excess air sucking up energy).

That said, a good development.

I'm sorry, cidi and mo, for bringing up the stratified charge business, for this is not the mode that this DiesOtto engine operates.
The article states that "all further emissions control in the DiesOtto engine is via a standard 3-way catalytic converter," meaning that GDI is used to spray fuel into the air during the compression stroke at stoichiometric ratio instead of lean-burn regime.
The efficiency gained in both HCCI and SI modes comes from engine down-sizing via turbocharging, thus allowing reduced pumping loss during low load limit operation.
The variable compression ability accounts for further increase efficiency in the high speed autobahn mode by raising compression at high engine speed or at low manifold pressure regime, and lowering the compression ratio at low engine speed but high manifold pressure regime in order to avoid engine knock.

Ethanol and water injection would be another way to permit higher compression ratio for improved efficiency at high engine speed.

Didn't make myself clear, litesong. PHEVs are right around the corner (actually here) whereas EVs are down the road a bit. Can't agree with you more that EVs are the ultimate solution. In the meantime, perfected ICEs are a big help.

Considering the fact that ICE-HEV has comparable well-to-wheel efficiency as BEV using electricity from the most efficient power plants (combined-cycle gas-fired), the ICE will be around for a very long time...until you can replace most power plants today with wind, solar or nuclear energy...

...but wait, wind and solar energy are not reliable enough to replace fuel-burning power plants...and then, there are means available today to synthesize transportation fuels from wind and solar energy at very high efficiency level from source to wheel,almost comparable to solar or wind electricity to inverter to grid then to charger then to rectifier then to battery then to power inverter then to motor then to wheel.

Although the term DiesOtto has been put forward as a catchy term for the operation it is timely to consider the fortunes of Diesel and Otto. Diesel suffered many problems in business and finally jumped overboard a ship to end his life. Otto had an equally tough time and died early in life. Ironically it was Gottlieb Daimler who rubbished his invention of what we call the Otto cycle engine. Daimler worked with Otto at Deutz and had a low opinon of Otto because he had no formal engineering education.

It was also Daimler who refused to accept the first reliable spark ignition system developed by Bosch, favoring a flame heated glowplug concept. Ref. "Vom Motor zum Auto" or "From Engines to Autos". It is therefore ironic that this DiesOtto named engine should come from a Daimler company.

By the way, no IC engines follow either the Diesel or Otto thermodynamic cycles. The closest theoretical cycle is the limited pressure cycle which is a combination of constant volume and constant pressure heat addition.

Rafael should consider that fuel enrichment at full load is required to protect the turbocharger in spark ingition engines. Diesel engines run lean even at full load and have substantially lower exhaust gas temperatures. They are also more efficient as a consequence. If that were not the case they would not be winning races like the Le Mans 24 hour would they?

Extracomment,

Thanks for the interesting bit of history. You've made a good point re. higher exhaust temp of gasoline engine, necessitating mixture enrichment for the turbocharge mode. But, turbocharged gasoline engine has low compression ratio around 8 or so in order to avoid detonation. This results in low expansion of combusted gas, hence high exhaust gas temp.

Now, what if you would raise the compression ratio in the high-speed turbocharged mode to 11 or higher, via the variable compression mechanism, instead, and use two-stage direct fuel injection instead of a single stage homogenous-charge-forming injection, in order to prevent detonaton. Inject half of the fuel early in the compression stroke, forming a mixture too lean for detonation, and then, inject the second half much later to help initiate ignition. There, no detonation, yet less PM given the partially homogenous charge. But, the higher compression ratio produces a much cooler exhaust due to higher expansion ratio for a given degree of peak combustion temperature. Your exhaust gas temp will still be higher than that of a Diesel, but hopefully low enough that you don't have to enrich your mixture, thereby wasting fuel, during the high-speed autobahn mode. Since you're closer to isochoric combustion than that of Diesel combustion, you can attain the efficiency of a Diesel with lower compression ratiio. Just a thought.

What do ya think?